This invention relates to digital decoders and more particularly to a digital error correcting decoder.
Error correcting codes play an important role in modern day communications. The technical literature is filled with articles on the theory and practical implementation of such codes.
In communication theory, the optimum decoder is one where the received waveform (message) is correlated with each of the possible messages of the set of messages. The correlation having the maximum value is chosen as the message. To implement such an optimum decoder, the received signal can be processed in parallel with M = 2.sup.K correlators, where K is equal to the number of code bits, or in series with one correlator. The first method has the disadvantage in the large number of components reqired, which increase exponentially with increasing K. The second method requires only one correlator, but the processing speed is increased exponentially with increasing K. Neither solution is practical for K greater than three or four. Consequently, a great deal of effort has been devoted to developing practical decoders with a minimum loss in theoretical performance.